White Rock Landform in Pollack Crater
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White Rock Landform in Pollack Crater

April 5, 2007

This image shows a portion of a relatively bright landform named "White Rock" on the floor of Pollack crater in the Sinus Sabaeus region of Mars.

Data from the Mars Global Surveyor Thermal Emission Spectrometer (TES) indicates that this landform is not anomalously bright, relative to other bright Martian regions. Further, the apparent brightness seen here is due to contrast with other materials on the crater floor.

Dunes and ripples are visible in the dark material between the bright ridges. Their orientations appear to be influenced by wind directionally channeled by the ridges. Material appears to have been shed from the white landform and deposited on the darker bedforms indicating that the light-toned outcrops break down into fine materials.

Its high albedo and location in a topographic basin have led to suggestions that White Rock is an erosional remnant of an ancient lacustrine evaporate deposit. Other interpretations include an eroded accumulation of compacted or weakly cemented aeolian sediment.

Observation Geometry

Image PSP_002244_1720 was taken by the High Resolution Imaging Science Experiment (HiRISE) camera onboard the Mars Reconnaissance Orbiter spacecraft on 18-Jan-2007. The complete image is centered at -8.0 degrees latitude, 25.0 degrees East longitude. The range to the target site was 263.1 km (164.4 miles). At this distance the image scale is 26.3 cm/pixel (with 1 x 1 binning) so objects ~79 cm across are resolved. The image shown here has been map-projected to 25 cm/pixel and north is up.

The image was taken at a local Mars time of 03:42 PM and the scene is illuminated from the west with a solar incidence angle of 57 degrees, thus the sun was about 33 degrees above the horizon. At a solar longitude of 168.7 degrees, the season on Mars is Northern Summer.

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